1. Field of the Invention
The invention relates generally to the rehabilitation or repair of waste water system components, such as manholes, sewer pipes, lift stations or clarifiers, through the application of a multi-layer liner. More particularly, the invention relates to the rehabilitation of such systems where the multi-layer liner is spray-applied and comprises at least a surfacer layer and a barrier layer. Even more particularly, the invention comprises such a liner where the surfacer layer is composed of a urethane foam, the barrier layer is composed of a polyurea and isocyanate polymer blend. Alternatively, the surfacer layer may be an epoxy and the barrier layer a polyurea foam. In a second embodiment, the invention relates to a multi-layer liner composed of a first barrier layer, a surfacer layer and a second barrier layer.
2. Description of the Prior Art
Deterioration of waste water system components is a severe and growing problem. Originally built of brick, block or concrete construction, these components develop leaks, cracks and holes due to age, erosion, corrosion and ground water intrusion. Leakage from old manholes and sewer lines contaminates the environment and sometimes results in catastrophic damage with respect to clean-up and repair costs.
Many concrete structures, such as containment areas or ponds, require a liner to prevent leakage of the contained material into the concrete and adjacent soil and to prevent corrosion or deterioration of the concrete from the material, which is often corrosive and/or toxic. Due to the size of most of these structures, a preformed liner is both impractical and expensive. Therefore, a spray on liner which may be applied relatively quickly, easily and at a reduced cost would be beneficial.
Since the cost of repairing the components is typically much less than the cost of replacement, many techniques have been developed to repair and rehabilitate waste water system components. For example, it is known to recast manholes and the like through the use of forms and poured concrete, such as shown in U.S. Pat. No. 5,032,197 to Trimble. Because this process is very labor intensive, many techniques are directed toward spray-applied liners. For example, Strong in U.S. Pat. No. 5,002,438 teaches the use of sprayed cement to form a liner inside the deteriorating structure. Spray-applied epoxy, acrylic or polyurethane liners are also known, as is the use of resin impregnated substrates, such as felt, as taught in U.S. Pat. No. 5,017,258 to Brown et al. The current spray-applied systems suffer from moisture, delamination, shrinkage and structural weakness problems resulting from the typical environment encountered in the repair operation.
U.S. Pat. No. 5,618,616 to Hume describes a technique and device for rehabilitating waste water system components wherein a multilayered liner is used to impart structural strength and integrity to the components. The multilayer liner of Hume is composed of a primer layer a first moisture barrier layer, a foam layer and a second moisture barrier layer. The primer layer is applied directly to the surface of the waste water system components and can be applied to a wet surface. Typically, the primer layer is an epoxy material.
It is an object of this invention to provide a technique and particular liner structure for repairing waste water system components which is spray-applied and does not suffer from the problems relating to moisture, delamination, shrinkage and structural weakness.
It is a further object to provide such an invention which increases the structural integrity of the repaired component due to the unique composition of the layers within the multi-layer laminate applied to the component.
It is still another object to provide such an invention which can be applied to any shape surface having any number of irregularities and that has a rapid cure time.